A computer file may be described as a block of arbitrary information, or resource for storing information, which is generally available to a computer program and is usually based on some kind of durable storage. A file is durable in the sense that it remains available for programs to use after the current program has finished. Application software may be described as a subclass of computer software that generally employs the capabilities of a computer directly to a task that a user wishes to perform. System software is typically involved in integrating a computer's various capabilities, but generally does not directly apply them in the performance of tasks that benefit the user. In this context the term application may refer to both the application software and its implementation. Each computer file acts independently and is manipulated independently. A program, like an operating system or an application window, may display one or more computer files.